The present invention relates to a solid-state image sensor device and a differential interface thereof.
With significant advances in digital technology in recent years, digital cameras have become prevalent in place of conventional film cameras that had been in widespread use. Designed with remarkable improvements in image quality, most of the latest models of digital cameras are capable of providing image formation performance superior to that of conventional film cameras. For use in digital cameras, there are mainly two kinds of solid-state image sensor devices; CCD (Charge Coupled Device) image sensors, and CMOS (Complementary Metal Oxide Semiconductor) image sensors.
To achieve higher functionalities in digital cameras, particular attention has been given to CMOS image sensors. In particular, intensive research and development has been conducted on digital output types of CMOS image sensors capable of outputting massive image data at high speed. With the use of a digital-output CMOS image sensor allowing high-speed output of massive image data, a digital camera will be usable not only for movie recording but also for a variety of shooting applications in combination with image processing. For example, in recording a momentary scene of a tennis racket hitting a ball or a close-up picture of a child's face just in front of a finish-line tape in an athletic meet, it will become possible to let a digital camera equipped with a digital-output CMOS image sensor judge when to click a shutter thereof in an automatic mode just by orienting the digital camera in the shooting direction of interest.
In operation of a digital-output CMOS image sensor, it is required to transfer massive data of images being taken to an image processing circuit block at high speed. To meet this requirement, the digital-output CMOS image sensor employs a plurality of ADC circuits arrayed with respect to image sensor columns and a plurality of differential interface circuits featuring a small amplitude such as LVDS (Low Voltage Differential Signaling) interface circuits capable of outputting pixel data at a fast speed corresponding to a high frame rate of digital imaging. Concrete examples of digital-output CMOS image sensor configurations are found in the patent documents 1 and 2 and the non-patent document 1 indicated below.
As described in the non-patent document 2 indicated below, the LVDS interface used in the digital-output CMOS image sensor can realize high-speed data transfer on the order of at least hundreds of Mbps with low power consumption and low noise including low EMI (Electro-Magnetic Interference) owing to high performance of noise suppression to ensure high reliability of data transmission.
Patent Document 1:
Japanese Unexamined Patent Publication No. 2000-333081
Patent Document 2:
Japanese Unexamined Patent Publication No. 2005-86224
Non-Patent Document 1:
S. Yoshihara, et al, “A 1/1.8-inch 6.4M pixel. 60 Frames/s CMOS Image Sensor with Seamless Mode Change,” IEEE JSSCC 41 (12), 2006
Non-Patent Document 2:
National Semiconductor Corporation, “LVDS Owner's Manual (3rd Edition), Chapter 1—Introduction to LVDS”, [online], December 2004, Internet <URL:http://www.national.com/JPN/appinfo/lvds/files/lvds_ch1.pdf>